Catalysis of hydrocarbons



R. E. 'BURK ET AL CATALY-SIS OF HYDROCARBONS Filed March. 27, 1943 Dec. 16, 1947.

Patented Dec. 16, 1947 CATALYSIS F HYDROCARBQNS Robert E. Burk and Everett C. Hughes, ClevelandHeights, Ohio, assignors to The Standard Oil Company, Cleveland Ohio, a corporation of Ohio Application March 27, 1943, Serial No. 480,804

.4 9 Claims. (Cl. ZEG-683.4)

This invention relates to the catalytic treatment of hydrocarbons to produce branched-chain hydrocarbons in the gasoline boiling range, such as iso-pentane, iso-octane, neo-hexane, 2,3'-di methyl butane, etc., which may be used as aviation gasoline base stock, with lead tetraethyl, or blended in ratios other than those of normal recovery.

It has been proposed heretofore to alkylate iso-paraiiins with olefins by a number of different processes. But the lso-parafllns of the desired molecular weight used in such processes do not occur normally in liberal amounts and must be formed from normal hydrocarbons by a separate and different process before they can be alkylated.

" In accordance with this invention it is possible to produce alkylation products of the desired configuration and boiling range from a wide variety of hydrocarbon raw materials and in a unitary process using a single catalytic material that is readily recoverable and reuseable.

It is an object of the invention to provide a unitary process of producing branched-chain hydrocarbons in the gasoline boiling range utilizing hydrogen uoride as the catalyst promoted 'by a minor amount of boron triuoride as the essential catalytic agent for forming lthe isoparaffins and for alkylating them with olefins.

A further object of the invention is to provide a process in which the same above described l catalytic material is not deleteriously affected by the process and may be recovered and rccyled through the various stages of the process indefinitely.

An additional object of the invention is to provide a process in which either normally gaseous and normally liquid hydrocarbons, and particularly both of them, may be used as the raw materials..

Still a further object of the invention is the provision of a process in which substantially all of the initial products are eventually converted into the wanted branched-chain products and in which those initial products not so converted in the rst pass are recycled further and converted.

In practicing the invention a normally gaseous hydrocarbon, preferably high in butanes; or a higher boiling fraction, such as a Cs cutor preferably a fraction boiling above 300 F. such as kerosene or gas oil; or preferably a mixture of both, is treated with hydrogen fluoride and a minor amount of boron trlfluoride under appropriate conditions to accomplish averaging, cracking,

isomerizing, and possibly some alkylating. The mixture is then treated to separate theahydrocarbons formed-as a result of the reactions referred to, from the major portion of the catalyst and the materials which are associated with it. The catalyst is returned to the reaction zone.

The separated hydrocarbons contain butanes, a major portion being iso-butane, and hydrocarbons of higher molecular weight. Depending on the composition of the feed, there may be some hydrocarbons of lower molecular weight than butanes. Some of the catalyst, including both hydrogen fluoride and boron triiluoride, may remain with the separated hydrocarbons.

The separated hydrocarbons are then fractionated to yield a C4 fraction containing the hydrogen fluoride and a smaller amount of boron trifluoride dissolved therein. The major portion of thel butane fraction will be isobutane. The higher boiling hydrocarbons, preferably those not comprised in the wanted product, may be returned to the reaction zone where they are further treated with the feed stock and subjected to such reactions as cracking and averaging. The lighter vboiling hydrocarbons, if any, also may be included in the C4 fraction, or they may be returned to the reaction zone, orotherwise disposed of.

The iso-butane containing fraction along with some fluorldes is then passed continuously to an alkylation zone and reacted with an olen. The

iiuorides carried with the iso-butane fraction serve as the catalyst, but they may be supplemented by an additional supply, particularly of hydrogen fluoride.

The products from the alkylation zone are then fractionated and the wanted branchedchain products may be separated on intermediate plates of the fractionator. The lighter products, such as butanes and any lighter boiling products and including the catalyst, aswell as heavier products, are separately returned to the reaction The normally gaseous hydrocarbon fraction preferred is butane which may contain some isobutane. Some pentanes, particularly iso-pentane may be included and under some conditions, depending on the reaction to be eiected in the reaction zone, this fraction may contain some propane, ethane, methane or mixture of any of them with each other or with the other gaseous hydrocarbons. -Renery gases containing butanes may be used t advantage and any olefns present in the gaseous fraction need not'be removed before feeding it into the reaction zone. The normally gaseous hydrocarbon fraction may be under pressure so that a part or all of it is liquid at the time `it is fed to the reaction zone.

The normally liquidmydrocarbon fraction may contain Ce and higher hydrocarbons; preferably it has a boiling point above 300 F., but may include gasoline, heavy naphtha. kerosene, gas oil, reduced crudes, crudes, etc. When aromatics are present in the liquid fraction they may be removed preliminarily by any suitable process, suchy' by selective solvent extraction, or by removal through reaction with the hydrogen iluoride-boron trifluoride catalyst. Alternatively, the stock may contain aromatics if suiilcieni; catalyst is present in the reaction `zone and if the conditions of the reaction are otherwise suitable. Unsaturates may be contained in the liquid as well as the gaseous fraction fed to the reaction zone.

Present in the reaction also is the catalyst comprising hydrogen fluoride in which boron trifluoride is dissolved. The temperature of the reaction mayvary from -22 to +392 F., preferably from about 32 F. to 150 F. The pressure is such as to keep the hydrogen uoride liquid at the temperature used, but may be any higher pressure than this if desired. The amount of hydrogen iluoride may be 5 to 300 volume percent, based on the hydrocarbons (as liquids), preferably to 150 volume percent. The amount of boron trifluorides may vary from a trace to 50 mol percent, based on the amount of hydrogen fluoride. It is convenient to control and measure the amount of boron trifluoride in terms of its partial pressure. The partial pressure may vary from 1 to 600, preferably 25 to 300, pounds per square inch. The amount of boron trifluoride (based on the amount of hydrogen fluoride) corresponding to a given partial pressure will depend on the total pressure and the temperature. However, the boron trifluoride (B. P. 150 F.) present at any temperatures of the reaction will exert a partial pressure and because of the convenience of measurement and control it is preferred to express the amount of boron trifluoride in terms of partial pressure. The partial pressure Within the range mentioned does not exceed the upper limit of 50 mol percent, based on the amount of hydrogen uoride.

The length of the reaction may vary depending on the materials used, the products wanted, the

amount of catalyst, temperature, etc'. The reaction time may involve a few minutes up to ten hours. The materials in the reaction zone are kept under agitation or otherwise in a state of intimate admixture. The operation may be batch or continuous and suitable apparatus to effect the same will be apparent to one skilled in the art from a consideration of this description. During the reaction boron trifluoride or hydrogen uoride may be added from the reserve supply 6, through the valve 'I and pipe 8. If desired the hydrogen iiuoride and boron trifluoride may be admitted separately from independentl supplies. The separate supply of boron trifluoride may be used to maintain the desired partial pressure of boron trifluoride.

During this phase of the process the hydrocarbons will undergo isomerizing, averaging, cracking and possibly some alkylating depending on the composition of the feed stocks, and the conditions of the reaction. For example, a major part of the butane may be isomerized to iso-butane; lower and higher hydrocarbons may be average, i. e., a molecule of a lower molecular weight hydrocarbon and a molecule of higher molecular weight hydrocarbon may form two molecules of an intermediate molecular Weight hydrocarbon which may then be isomerized or otherwise reacted; higher boiling hydrocarbons may be cracked and the cracked products may be isomerized, averaged or further cracked. If either feed stock contains unsaturates, alkylation of isp-paramos or any aromatics present may take place.

After the reaction is com-plete the mixture is withdrawn through a conduit 9 andiintroduced into a settling tank I0 Where the mixture will stratify into two layers.

The bottom layer contains the major portion of the catalyst and some hydrocarbons, generally unsaturates and-aromatics which form a complex with the catalyst. The bottom layer may be withdrawn through a conduit II and passed to a separator I2 where the catalyst may be separated by heatingl and returned to the reaction` zone through the pipe I3, or to a later stage of the process through the pipe 3l.r This action may be controlled by Valves I5 and I6. The products remaining after the removal of the catalystmay be tre'ated to separate any fraction, such as aromatics, if desired. In general these products'comprise unsaturates which possess properties similar to a good drying oil.

The top layer, which contains iso-butane and higher and any lower boiling hydrocarbons, depending on the initial reactants and the reaction conditions, and some of the catalyst, is passed through a conduit I'I to a fractionator I8. The operation of the fractionator may be Varied. In any event the C4 fraction containing a major portion of iso-butane and some normal butane is separated and sent through the conduit I9. If lower boiling products are separately fractionated, they may be returned through the conduit 20, Valve 2| and conduit 22 to the initial feed, or through conduit 23 and valves 24 and 25 and drawn off. Under some circumstances it may be unnecessary or undesirable to separate the light boiling hydrocarbons from the butanes since the former will be returned to the reaction zone at any event later in the process. In such a variation, the valve 26 may be closed and the fractionator seperated to take the butanes and all lighter products through conduits 20 and 23, valve 24 and conduit I9.

- The products boiling higher than the butanesi,

are withdrawn from the fractionator through the conduit 21 and may be returned to the reaction zone through the conduits 28 and 29. Alternately, they may be sent through the conduit 30 for further fractionation. Valves 3| and 32 may be used to control the ow of these products.

The following specific example is illustrative of this phase of the process:

One volume of dearomatized kerosene derived from vPennsylvanie. crude, and two volumes of butane containing 16% iso-butane, are fed into the reaction mixer initially. These are treated with one volume of liquid hydrogen fluoride and boron trifluoride in an amount to provide a partial pressure of 150 pounds per square inch, this amount being 0.534 part of boron trifiuoride for each part of kerosene. The reaction was permitted to proceed for two hours at a total pressure of 210 pounds per square inch and at a temperature of 90 F.

Following this, the reaction mixture was stratifled in the settling tank l0. "Ihe lower layer was found to obtain 7.15% of the hydrocarbons fed to the reaction zone. The upper layer contained 37.2% iso-butane, 20% n-butane, 27.75% boiling within the range of 70410 F., 6.15% boiling above 410 F., and 1.75% propane.

The isoand normal-butane, comprising about 57% of the initial feed, may be fractionated and sent through the conduit I9 for alkylation. In this instance, in view of the small amount of propane formed, the propane may be sent with the butane fraction, which may be withdrawn from' the fractionat'or through the conduits 20 and 23, valve 24 and conduit I9. The heavier-fraction, comprising about 34% initial feed, is returned through the conduit 21 for further reaction, or through the conduit 30 to the fractionator 39.

It will be apparent that the above results may be considered only illustrative, since the character of the reacting ingredients constantly changes because of the stock to be recycled. This will eventualy reach a substantial equilibrium, however, to provide good yields of iso-butane.

The iso-butane containing fraction is then passed through the conduit I9 to an alkylation zone 33 and an olefin also is admitted. The olefln can be introduced with advantage through the conduit 34 into the conduit I9 to become premixed with the iso-butane fraction. The isobutane also may be used to extract the olen from a gas in which olefin is contained. The isobutane fraction carries with it a small amount of hydrogen fluoride and probably some boron trifluoride and these may be enough to effect the alkylation. Generally the amount of boron trifluoride is sufiicient. Some alkylation reactions will proceed with hydrogen iiuoride without boron trlfluoride, but a small amount facilitates them. In other alkylation reactions the presence of boron trifiuoride is essential. Thus it is not essential in all instances that boron triiluoride be contained in the iso-butane fraction. An additional amount of hydrogen fluoride may be admitted from the reserve supply 35 through valve 36 and conduit 31. Also some of the catalyst from the separator I2 may be admitted through the valve I6 and conduit 31. Alternatively a part or all of the catalyst containing lower layer can be introduced into the alkylating step through the valve Ila and conduit IIb without separation of the catalyst from the hydrocarbons,

The olen admitted to the alkylation stage at 34 preferably is ethylene, propylene or butylene.

The iso-butano should be present in an amount of 2 to 15 mol per mol of olefin to insure the complete reactlon of the olefin and to repress polymerization of the olefin. The unreacted isobutane is simply recycled.

The alkylation operation is carried out under about the same temperature and pressure conditions as in the reaction zone.

The products from the alkylation zone are then removed through a conduit 38 and fractionated at 39. The wanted products are withdrawn through the valves 40 and conduit 4i and sent to storage 42.

The hydrocarbons and the fluoride catalyst may be separated and only` the hydrocarbons fed to the fractionator 39. The uoride catalyst may be recycled to the alkylation step or part of it may be carried to the reaction zone 5.

The butanes in the fraction in the conduit I9 (and any lighter boiling hydrocarbons) which are not alkylated, are returned through conduit 43 to the initial supply I, or through thevalve 43a and conduit 43h to the alkylation reaction. The fractionator is so operated that all of the hydrogen fluoride and boron trifluoride is returned with this lighter fraction to the reaction or alkylation zone, because the fiuorides boil at a lower temperature than that of the wanted products. The heavier products, boiling higher than those of the wanted products, are returned through conduits 44 and 29 to be added to the heavier feed stock. As illustrative of this phase of the process, the following example is given:

The butane fraction introduced in the alkylation zone 33 through the 'conduit I9 is alkylated with ethylene. The molal ratio of iso-butane to ethylene is 12:1. The excess of the iso-butane is returned through the conduit 43 and recycled. The alkylation reaction was carried out at a temperature of 34 F., in the presence of 11.4% by Weight of boron trifiu-oride, and 18.7% by weight hydrogen fluoride based on the total hydrocarbons. The reaction time was 9 minutes. The products of the alkylation (based on the amount of ethylene used which gives a theoretical yield of 307%) were iso-pentane, 24%; neo-hexane, 31.8%; 2,3-dimethyl butane, 93%; higher boiling hydrocarbons 43%; which are withdrawn through the conduit 4I. ing above 300 or 400 F. are returned through the conduit 44; these amount to but a very small part of the hydrocarbons boiling above 2,3-dimethyl butane.

them rather than recycle them., 'they may be` withdrawn through the valve 25 at any time. Since they may contain a part of the catalyst, it may be desirable to recover this by means of an absorption and desorption system, before using the gases as fuel or for any other purpose.

Similarly the heavier product exiting from 44 may be fractionated to remove any products that are not to be returned to the reaction zone 5. The operations in this regard will depend on the raw materials available and the eihciency re- The hydrocarbons boil.-`

quired and economic factors.l Generally. however, it will be seen that all of the products are converted to the branched-chain products of thc desired molecular weight. By continuously removing them from the reaction zone, and by continuously removing:I the iso-butane and other isoparafns by the alkylation process, the equilibrium is shifted in such a way as to be able to convert the great portion of the raw materials to the wanted products upon suitable recycling. This is made possible because of the unique characteristics of the catalyst employed.

The invention is capable of many detailed modications, as will be apparent to one skilled in the art. and we intend all of such modifications to be included as are within the scope of our claims.

We claim: 1

1. A process of producing hydrocarbons in the gasoline boiling range by processes of averaging and alkylating, which comprises subjecting a mixture of a normally liquid hydrocarbon fraction and a normally gaseous hydrocarbon fraction containing a normal hydrocarbon to the action of a liquid catalyst comprising liquid hydrogen uoridc in which is dissolved not over 50 mol per cent of boron trifiuoride (based on the hydrogen n fluoride), and continuing the reaction under averaging conditions including a pressure to maintain the hydrogen uoride liquid and at a temperature and for a period of time while adjusting the partial pressure of the boron trinuoride to produce averaged hydrocarbons intermediate said normally gaseous and said normally liquid hydrocarbon Yfractions and also to isomerize the normal hydrocarbon contained in said normally gaseous hydrocarbon fraction, separating said isomerized hydrocarbon, transferring said isomerized hydrocarbon to an alkylation zone together with the uorides which separate therewith from the averaging reaction, alkylating at least part thereof with an olefin in the presence of the above-defined catalyst comprising said uorides separated from the averaging reaction.

2. A process of producing hydrocarbons in the gasoline boiling range by processes of averaging and alkylating, which comprises subjecting a mixture of a normally liquid hydrocarbon fraction and a normally gaseous hydrocarbon fraction containing a nor-*nal hydrocarbon to the action of a liquid catalyst comprising liquid hydrogen uoride in which is dissolved not over 50 mol per cent of boron trifiuoride (based on the hydrogen fluoride), and continuing the reaction under averaging conditions including a pressure to maintain the hydrogen fluoride liquid and at a temperature and fora period of time while adjusting the partial pressure of the boron trifluoride to produce averaged hydrocarbons intermediate said normally gaseous and said normally liquid hydrocarbon fractions and also to isomerize the normal hydrocarbon contained in said normally gaseous hydrocarbon fraction, separating said isomerized hydrocarbon, transferring said isomerized hydrocarbon to an alkylation zone together with the uorides which separate therewith from the averaging reaction, alkylating at least part thereof with an olefin in the presence of the above-defined catalyst comprising said fluorides separated from the averaging reaction, and separating said intermediate hydrocarbons and said alkylate in a single fractionating operation.

3. A process of producing hydrocarbons in the gasoline boiling range by processes of averaging and alkylating, whichy comprises subjecting a mixture of a normally liquid hydrocarbon fraction boiling in the gasoline-kerosene range, and a normally gaseous hydrocarbon fraction containing normal butane, to the action of a liquid catalyst comprising liquid hydrogen fluoride in which is dissolved not over 50 mol per cent of boron triuoride (based on the hydrogen fluoride), and continuing the reaction under averaging conditions including a pressure to maintain the hydrogen fluoride liquid and at a temperature and for a period of time while adjusting the partial pressure of the boron trifiuoride to produce averaged hydrocarbons intermediate said normally gaseous and said normally liquid hydrocarbon fractions and also to isomerize the normal butane contained in said normally gaseous hydrocarbon fraction, separating said iso-butane, transferring said iso-butane to an alkylation zone together with the uorides separated therewith from the averaging reaction, alkylating at least a part thereof with an 'olefin in the presence of the same above-identied catalyst comprising said fluorides separated from the averaging reaction.

4. A process of producing hydrocarbons in the gasoline boiling range by processes of averaging and alkylating, which comprises subjecting a mixture of a normally liquid hydrocarbon fraction boiling in the gasoline-kerosene range, and a butane fraction containing normal butane, to the action of a liquid catalyst comprising liquid hydrogen fluoride in which is dissolved not over 50 mol per cent of boron trifiuoride (based on the hydrogen fluoride), and continuing the reaction under averaging conditions including a pressure to maintain the hydrogen uoride liquid and at a temperature and for a period of time while adjusting the partial pressure of the boron trifluoride to produce averaged hydrocarbons intermediate said butane and said: normally liquid hydrocarbon fractions and also to isomerize normal butane contained in said butane fraction, separating said iso-butane, transferring said isobutane to an alkylation zone together with the fluorides which separate therewith from the averaging reaction, alkylating at least a part thereof with-an olen of not over 4 carbon atoms in the presence of the above defined catalyst comprising said fluorides separated from the averaging reaction, and separating said intermediate hydrocarbons and said alkylate in a single fractionating operation. .'r

5. A process of producing hydrocarbons in the gasoline boiling range by processes of averaging and alkylating, which comprises subjecting a mixture of a normally liquid hydrocarbon fraction boiling in the gasoline-kerosene range, and a butane fraction containing normal butane, to the action of a liquid catalyst comprising liquid hydrogen uoride in which is dissolved not over 50 mol per cent of boron trifiuoride (based on the `hydrogen fluoride), and continuing the reaction under averaging conditions including a pressure to maintain the hydrogen fluoride liquid and at a temperature and for a period of time while adjusting the partial pressure of the boron trifluoride to produce averaged hydrocarbons intermediate said butane and said normally liquid hydrocarbon fractions and also to isomerize normal butane contained in said butane fraction, separating said iso-butane, transferring said isobutane to an alkylation zone together with the iiuorides which separated therewith from the averaging reaction, alkylat'ing said iso-butane with ethylene in the presence of the above-defined catalyst comprising said separated fluorides.

6. A process of producing hydrocarbons in the gasoline boiling range by processes of averaging and alkylating, which comprises subjecting a mixture of a normally liquid hydrocarbon fraction boiling in the gasoline-kerosene range, and s, butane fraction containing normal butane, to the action of a liquid catalyst comprising liquid hydrogen uoride in which is dissolved not over 50 mol per cent of boron triuoride (based on thei hydrogen fluoride), and continuing the reaction under averaging conditions including a pressure to maintain the hydrogen fluoride liquid and at a temperature and for a period of time while adjusting the partial pressure of the boron trifiuoride to produce averaged hydrocarbons intermediate said butane and said normally liquid hydrocarbon fractions and also to isomerize normal butane contained in said butane fraction, separating said iso-butane, transferring said isobutane to an alkylation zone together with the iluorides which separated therewith from the averaging reaction, alkylating said iso-butane with a butylene in the presence of the above-dened catalyst comprising said separated fiuorides.

7. A process of producing hydrocarbons in the gasoline boiling range by processes of averaging and alkylating, which comprises subjecting a mixture of a normally liquid hydrocarbon fraction and a larger liquid volume of a normally gaseous hydrocarbon fraction containing a normal hydrocarbon, to the action of a liquid catalyst comprising liquid hydrogen iluoride in which is dissolved not over 50 mol per cent of boron trifiuoride (based on the hydrogen fluoride), and continuing the reaction under averaging conditions including a pressure to maintain the hydrogen fluoride and the normally gaseous hydrocarbon fraction liquid and at a temperature and for a, period of time while adjusting the partial pressure of the boron trifluoride to produce averiaged hydrocarbons intermediate said normally gaseous and said normally liquid hydrocarbon fractions as a res'ult of reactions which take place only in the presence of both said fractions, and also to isomerizethe excess of the normal hydrocarbon contained in said normally gaseous fraction, separating the hydrocarbons as an upper layer from the major portion of the fluoride catalyst as a lower layer, separating the isomerized hydrocarbon from the upper layer together with i the uorides from the averaging reaction contained in said upper layer, and alkylating said isomerized hydrocarbons 'with an olen in the presence of a catalyst comprising the iluorides separated from the averaging reaction.

8; A process of producing hydrocarbonsin the gasoline boiling range by processes of averaging and alkylating, which comprises subjecting a mixture of a normally liquid hydrocarbon fraction boiling above the gasoline range, and a larger liquid volume of a normally gaseous hydrocarbon fraction containing normal butane, to the action of a liquid catalyst comprising liquid hydrogen fluoride in which is dissolved not over 50 mol per cent of boron trifluoride (based on the hydrogen fluoride). and continuing the reaction under averaging conditions including a pressure to 10 maintain .the hydrogen fluoride and the normally gaseous hydrocarbon fraction liquid and at a temperature and for-a period of time while adjusting the partial pressure of the boron triuoride to produce averaged hydrocarbons intermediate said normally gaseous 'andsaid normally liquid hydrocarbon fractions as a result of reactions which take place only in the presence of both saidv fractions, and also to isomerize the excess of the normal butane contained in said normally gaseous fraction, separating the hydrocarbons as an upper layer from the major portion of the fluoride catalyst as a lower layer, separating the iso-butane from the upper layer together with the fiuorides from the averaging reaction contained in said upper layer, and alkylating said isobutane with an olen in the presence of a catalyst comprising the fluorides separated from the averaging reaction.

9. A process of producing hydrocarbons in the gasoline boiling range by processes of averaging and alkylating, which comprises subjecting a mixture of a normally liquid hydrocarbon fraction boiling above the gasoline range, and a larger liquid volume of a butane fraction containing normal butane, to the action of a liquid catalyst comprising liquid hydrogen fluoride in which is dissolved not over 50 mol per cent of boron trifiuoride (based on the hydrogen fluoride), and continuing the reaction under averaging conditions including a pressure to maintain the hydrogen iluoride and the butane fraction liquid and at a temperature and for a period of time while adjusting the partial pressure of the boron trifluoride to `produce averaged hydrocarbons intermediate said butane and said normally liquid hydrocarbon fractions as a result of the reactions which take place only in the presence of both said lfractions, and also to isomerize the excess of the normal butane, separating the hydrocarbons as an upper layer from the major portion of the fluoride catalyst as a lower layer, separating the iso-butane from the upper layer together with the fluorides from the averaging reaction contained in said upper layeryand alkylating said iso-butane with an olen in the presence of a catalyst comprising the fluorides separated from the averaging reaction.

ROBERT E. BURK. EVERE'IT C. HUGHES.

REFERENCES CITED vIlhe following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,325,122 Ipatieir et al July 27, 1943 2,293,705 Block Aug. 25, 1942 2,303,663 Shankland Dec. 1. 1942 2,315,197 Goldsby et al. Mar. 30, 1943 2,220,092 Evering et al.` Nov. 5. 1940 2,240,134 Egloi Apr. 29, 1941 2,348,317 Gibson Apr. 25. 1944 2,266,012 DQuville et al Dec. 16, 1941 2,393,857 Frey Jan. 29, 1945 Certificate of Correction Patent No. 2,432,505. December 1e, 1947.

ROBERT E. BURK ET AL.

It is hereby certied that errors appear in the printed specificetion of the above numbered patent requiring correction as follows: Column 3, line 44, after the word reaction insert zone; column 10, list of references cited, under United States Patents,.lne 65, for 2,348,317 read 2,347,317; and that the said Letters Patent should be read with these corrections therein that vthe same may conform to the record of the case in the Patent Office.

Signed and sealed this 16th day of March, A. D. 194g.

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

